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Preferment timing

May 21, 2012 - 3:04pm

petercook

Preferment timing

Hello, I am having a difficult time telling EXACTLY when my poolish has reached the peak of development. Didier Rosada says that the poolish should dome slightly and just start to recede but mine never domes. I follow the instructions to the letter bu t no dome. Hmm?

50 gram whole wheat flour

150 gram of un-bleached bread flour

200 gram of bottled water

.1 gram of instant yeast (yes, that's 1/10th of one gram)

My poolish, rests at room temp aprox 70 F. , for 14 hrs, it rises nicely and is covered with bubbles but never domes. As I am trying to develop the max amount of homofermentive bacteria in the poolish I thnk timing is critical. Any help would be muct appreciated. Thank You.

I don't see any sourdough starter in your formula. Only yeast. So you will have NO bacteria in your poolish. Not homofermentative, not heterofermentative, not active, not passive, not subjunctive. NO bacteria.

I don't know if you use additional yeast for the final dough, but your poolish will be adequate to make bread when it has lots of little bubbles on top. The EXACT PEAK is a few hours long.

Doc Dough,I'm sorry to disagree with you but every bread author that I have on my shelf (Didier Rosada, Rose levy Beranbaum, Daniel T Di Muzio) says that lactic acids, acetic acids, homofermentive bacteria and heterofermentive bacteria all are produced with-in a preferment. If, for example I wanted to produce a mildly flavor loaf I would make a poolish (100% hydration) and use the tinyest amount of yeast. I would then allow it to ferment at a temp of 80 F. Thus the poolish would contain a very high concentration of homofermentive bacteria. If I wanted to produce a more sharply flavored loaf I might make a sponge (60% hydration) and let it ferment at 60 F thus producing mostly heterofermentive bacteria. Of course no preferment is PURELY one type of bacteria. My original question concerned how to tell exactly when my preferments are at their peak.

I regularly make a very similar poolish. It does not truly "dome" as the mixture is too thin for that but it does peak in its own subtle way. Just past peak activity is marked by a bit of a depression in the center of the bowl. The surface is, at that time, covered with very fresh bubbles and the center is a tiny bit concave instead of flat or slightly convex. It is subtle but positively detectable. Hope this helps,

When you make a poolish that builds on a starter containing LAB, then you will get LAB in your bread. If your starter has a pH of less than 5, there will be no Leuconostoc. If you start a poolish with yeast only, there is not sufficiant time to multiply up the naturally occuring bacteria in your flour to really significant levels in 14 hrs. If you innoculate with yeast that contributes 10E5 CFU/gm and you have at most 10E2 CFU/gm of LAB, the ratio of yeast to LAB will remain somewhere around 1000:1 in your poolish and in a healthy sourdough starter the ratio of yeast to LAB is somewhere in the vicinity of 1:100 so you need an additional factor of between 1000 and 100,000 to support your claim. So while I am willing to listen to the argument, you have to present evidence that either there is more LAB in the flour than the data supports, that the growth rate is higher than the models predict, or that there is another source of LAB that I have not accounted for. Give it your best shot.

Because I am not a food scientist all I can do is repeat what I have read in my baking books: They all say that we can develop homofermentive and/or heterofermentive bacteria in our preferments. The yeast and bacteria BOTH feed on the simple sugars produced by the enzyme amalyse and since the yeast feeds much faster than the bacteria (the race is on) we must some how slow down the yeast, hence we use tiny, tiny amounts of yeast so that the bacteria has a chance to develop. Also we can reduce the fermentation temp thus slowing down the yeast. I do not use any starter (sourdough) in my preferments.

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